This invention relates to the corrosion protection of pipelines consisting of iron-based, especially cast-iron, pipework elements. By "pipework elements" is meant the pipes as well as their various accessories, such as elbows, couplings, etc. The invention applies principally to buried pipelines, but may also be used in the case of overground pipelines.
The soil corrosion of ferrous metals is a phenomenon whose nature is different from atmospheric corrosion, and essentially consists of the creation of oxidation zones electrically associated with reduction zones which may be located some distance away. Localized and consequently significant deterioration of the ferrous metal therefore occurs.
The anti-corrosion protection of buried pipework elements is thus particularly difficult, the more so as terrains are heterogeneous and of very diverse types, as the pipework elements, depending on their use, convey fluids at different temperatures, modifying the corrosion conditions, and as the handling of the pipework elements intended to be buried frequently leads to damage at various places on their external surfaces.